LAUSR

Nitrogen is the most important element required for plant growth and development and is the primary nutrient limiting sugarcane production. Field experiments under rainfed condition and some periods with high temperature (above 35 oC) were carried out during 2014-2015 at the municipality of Ocampo, Tamaulipas, Mexico. The objective of the study was to determine the effect of varying doses of nitrogen fertilizer on leaf photosynthesis, plant growth, total chlorophyll, and juice quality of sugarcane commercial variety Mex 79-431 in the second ratoon crop. Six nitrogen doses (0, 60, 90, 120, 150, and 180 kg N ha ) were tested and applied as urea 60 days after harvest, at the beginning of the rainy season. The results of the experiment indicated that the application of nitrogen in ratoon crop had a positive effect on growth and development. It is important to note that further studies are required on the subject, including timing of nitrogen application, application method, soil types, other doses, and other genotypes in the region. The maximum photosynthetic rate (27.68 μmol CO2 m -2 s) was attained at PAR 1500 μmol m s with 90 kg N ha. The highest yield was recorded in ratoon crop with a dose of 120 kg N ha. At harvest, the juice quality did not show significant variations among the treatments imposed.